The present invention relates to a selective light-transmitting laminated film which transmits visible rays but reflects infrared rays. More particularly, the present invention relates to a selective light-transmitting laminated film having improved resistance against abrasion, light, weather and heat.
There has been known a laminated film comprising an organic polymer film vacuum-deposited with a thin layer of a metal such as aluminum, silver, copper or gold for the purpose of transmitting visible rays and reflecting infrared rays. Those laminated films are generally coated with a protective organic polymer layer having a thickness of 1-100.mu. applied to the metal surface for preventing the thin metal layer from scratch, stain or oxidation. Infrared ray reflectance of such a laminated film depends on the thickness of said metal layer. For obtaining a high infrared reflectance, the thickness of the metal layer must be increased. However, if the infrared reflectance is increased, visible ray transmission is inevitably decreased seriously to cause an insufficient lighting and unclear recognition of substances. Further, if the infrared reflectance is to be increased as described above, visible ray reflectance is also increased, whereby unpleasant reflected light diverges outside.
For overcoming the above defects, there has been known a process wherein the surface of said thin metal layer is coated with inorganic dielectrics having a high refractive index such as titanium oxide, bismuth oxide or zinc sulfide having a thickness of several hundred angstroms to form so-called anti-reflection layer, thereby decreasing the visible ray reflection, and increasing the transparency. Those inorganic dielectrics are applied to the thin metal layer surface by a physical film-forming means such as vacuum evaporation or sputtering or a chemical film-forming means such as solution coating or chemical vacuum deposition. However, if the above single metal compound is used as the anti-reflection coating in the form of a film having a large surface area, it has poor mechanical properties such as low abrasion resistance and poor flexibility and it is easily peeled off from the substrate by abrasion or bending. There has been proposed a method of improving those mechanical properties by incorporating an organic substance such as an organic titanate or organic silicate therein. However, problems still remain in that properties such as light resistance including ultraviolet resistance, weather resistance and heat resistance are deteriorated. Particularly, in order to obtain a film of a large surface area at low costs, the film must be formed at a high speed. However, as the film-forming speed is increased, the above defects become remarkable.